This invention relates to a process for obtaining sealed electric passages within insulating bodies formed at least partially from a metallic oxide. Such sealed passages form electrical connections between elements placed on either side of a wall and traverse the insulator forming such wall in a manner such that no mass transfer may occur between the media located on either side of the wall. The degree of sealing required here is that which is found in vacuum techniques such as is used in radio or television tubes, light bulbs and relays operating under vacuum or within special atmospheres.
The prior art includes three known methods for obtaining such passages which respond to the requirements:
(1) Embedding the conductors in a thermoplastic or thermosetting insulation, resin or synthetic rubber, etc.
(2) Providing the passages through a metallic member the conductors being then fastened thereto by glass beads.
(3) Providing the passages in an insulating member of glass or ceramic provided with metallized holes in which the conductors are fixed by soldering or brazing.
The first of these methods is often insufficient since most plastic materials or other synthetic insulators exhibit generally either an undesirable porosity or the capacity to absorb gas or vapor.
The second solution is faced with the difficulty of adapting the thermal expansion coefficients of the metals and glasses used. Such passages are moreover very sensitive to mechanical stress.
The third among these prior art solutions is particularly difficult to use since the solder and brazing materials have coefficients of expansion generally much higher than glass and ceramic and only through adoption of a special assembly geometry will it be possible to obtain an acceptable result.
This invention has for its object to provide a process for obtaining electric passages which are completely sealed and enable the avoidance of the previously-mentioned difficulties without requiring the collecting and assembling of elements of a different nature.